2nd to 3rd gearchange

M37UK · Post by **M37UK** » Fri Oct 24, 2008 12:49 pm

Hi folks, I am new to this group and have recently aquired my 1952 M37. I have been reading, with great interest, the articles in this forum.

Now, my question is, I am finding it really difficult to change from 2nd to 3rd gear without it sounding like I am feeding a box of spanners into a lathe.
Sometimes it seems to engage no problem but other times I have to miss out 3rd all together and go straight to 4th.
Any advice would be much appreciated.
I have tried the double-clutching method but it doesnt seem to make much difference.

Cheers,

Stuart

MSeriesRebuild · Post by **MSeriesRebuild** » Fri Oct 24, 2008 1:10 pm

M37UK wrote:Hi folks, I am new to this group and have recently aquired my 1952 M37. I have been reading, with great interest, the articles in this forum.

Now, my question is, I am finding it really difficult to change from 2nd to 3rd gear without it sounding like I am feeding a box of spanners into a lathe.
Sometimes it seems to engage no problem but other times I have to miss out 3rd all together and go straight to 4th.
Any advice would be much appreciated.
I have tried the double-clutching method but it doesnt seem to make much difference.

Cheers,

Stuart

This is a very typical issue with the early transmissions, either the snap ring is off the end off the main shaft or worst case the groove is broken out of the shaft. Either case a full rebuild DONE CORRECTLY is the only sure fix.

Lifer · Post by **Lifer** » Fri Oct 24, 2008 6:11 pm

As Charles implies, your transmission's synchronizers are not doing their job and an overhaul is in order. Until you can get the parts and get it fixed, you may find that double-clutching will make shifting easier.

M37UK · Post by **M37UK** » Sat Oct 25, 2008 5:20 am

Oh dear, not exactly what I wanted to hear but thanks for your help guys.

MSeriesRebuild · Post by **MSeriesRebuild** » Sat Oct 25, 2008 6:36 am

M37UK wrote:Oh dear, not exactly what I wanted to hear but thanks for your help guys.

A little more time to respond today, the snap ring & ring groove issue is very common in the early NP trans. The later NP420 is of better design & does not give this problem. The early design only has 1 snap ring that holds everything including second gear & forward on the main shaft. Once this failure happens, all gears are allowed to slide forward & move around on the shaft. This causes the hard shifting, simply because the gears are not held where they need to be to allow proper meshing. The thing to do is not continue driving it until this situation is checked out & fixed. Continuing to drive will absolutely destroy the trans from within. We've seen this problem in these transmissions lots of times, have seen a few totally destroyed when vehicles were continually driven until catastrophic failure occured. I know this isn't good news, but it is proven fact & good advice, check it out now.

Feel free to e-mail us via the website below if we can assist you with how to check it out.

Rail man · Post by **Rail man** » Sat Oct 25, 2008 8:15 am

M37UK wrote:Oh dear, not exactly what I wanted to hear but thanks for your help guys.

I had a similar problem with my trans. found a small pin in the top cover was broken. The pin keeps the ball in the lever from rotating horizontally, It will only allow the ball to rotate vertically this is what changes the shifter from the 1st &2nd fork to the 3rd & 4th fork.I found that if I reach far enough to the right with the shifter 3rd was there. The repair will require total disassembly of the top cover. My top cover was damaged inside and would not accept new parts, so I drilled the hole for the pin out and topped it for 7/16 NC. I then cut the head off the bolt, turned the end of the bolt down to about 5/16 (you'll need to mic. the slot in the ball) screwed it in adjusted the depth locked it down with a nut. Also I cut a screw driver slot in the end of the bolt.

MSeriesRebuild · Post by **MSeriesRebuild** » Sat Oct 25, 2008 9:00 am

Rail man wrote:
M37UK wrote:Oh dear, not exactly what I wanted to hear but thanks for your help guys.

I had a similar problem with my trans. found a small pin in the top cover was broken. The pin keeps the ball in the lever from rotating horizontally, It will only allow the ball to rotate vertically this is what changes the shifter from the 1st &2nd fork to the 3rd & 4th fork.I found that if I reach far enough to the right with the shifter 3rd was there. The repair will require total disassembly of the top cover. My top cover was damaged inside and would not accept new parts, so I drilled the hole for the pin out and topped it for 7/16 NC. I then cut the head off the bolt, turned the end of the bolt down to about 5/16 (you'll need to mic. the slot in the ball) screwed it in adjusted the depth locked it down with a nut. Also I cut a screw driver slot in the end of the bolt.

I've seen this situation many times also, the best fix for this is to replace the top cover assembly. What you have is easily recognized by excessive free play in the shift lever & can be visually seen by simply having a good external look at the outside of the tower. I hate to be the bearer of sad news, but the fix you have attempted is merely a band-aid on a death sentence. We've had countless transmissions come here with the same fix you have attempted, it is always short lived & if you don't go ahead & fix this thing right, further damage will result. New top cover assemblies for the early style trans are easy to install & not that costly. Way cheaper than ruining a whole transmission which will be the end result. You should also have a look inside to be sure the snap ring issue isn't the underlying cause of your problem as well, it very well could be. Trying to shift with the shift tower problem that you have had places tremendous stress on the main shaft sliding gears & synchronizer assemblies. Many times it is followed by the main shaft snap ring or groove failure as a result of this added stress.

M37UK · Post by **M37UK** » Sat Oct 25, 2008 12:58 pm

Thanks again folks for your input. I maybe should have mentioned earlier that I have a Canadian M37. Does this make any difference to your diagnostics?
I had a closer look at the plate on the trans and it has, what looks like,
a service plate from a company called The Gear Centre in Edmonton. It also states on the plate that the box is a T98 ???? The service took place in '99.

Any clues?

Cheers

Stuart

MSeriesRebuild · Post by **MSeriesRebuild** » Sat Oct 25, 2008 5:21 pm

Yes, this absolutely makes a difference, has a totally different trans if original. A T98 sounds like you may have a Warner trans. If so, I would say your problem is much more apt to be a bad sybchronizer. The Canadian trucks usually have an ACME gear box though.

Lifer · Post by **Lifer** » Sat Oct 25, 2008 6:33 pm

Dang!! I'm amazed at how much I can still learn at my age! Once again, I'll yield to experience. After reading Charles' more detailed post, perhaps double-clutching until you can get around to fixing the problem isn't such a great idea. Thanks, Charles!

.

M37UK · Post by **M37UK** » Sun Oct 26, 2008 12:02 am

Charles, whats the best way to properly identify the trans?

Stuart

MSeriesRebuild · Post by **MSeriesRebuild** » Sun Oct 26, 2008 9:32 am

M37UK wrote:Charles, whats the best way to properly identify the trans?

Stuart

Post a photo here, I'll see what I can figure out or maybe someone will recognize it.

Randy N · Post by **Randy N** » Sun Oct 26, 2008 2:08 pm

I have a service manual for the Cdn trucks and can scan some pages for you if need be.
They are almost identical to the US version except for the transmisssion as Charles has mentioned, the PTO if it has a winch, the 251 engine and them some other body related minor differences .
Regards

jbxx · Post by **jbxx** » Sun Oct 26, 2008 3:36 pm

Steuart, check off topic stuff!
J.B.

Randy N · Post by **Randy N** » Sun Oct 26, 2008 8:31 pm

I just checked my repair manual. In the specifications it lists transmission make: Canadian Acme Model T98.
The PTO if it has one is Canadian Acme Model 4867
Cheers

2nd to 3rd gearchange

2nd to 3rd gearchange

Re: 2nd to 3rd gearchange

Go Dons'